1. Field of the Invention
The present invention relates generally to fluid delivery systems for supplying fluids during medical diagnostic and therapeutic procedures and, further, to medical connectors for use with such fluid delivery systems and fluid paths used in fluid delivery systems.
2. Description of Related Art
In many medical diagnostic and therapeutic procedures, a medical practitioner such as a physician injects a patient with a fluid. In recent years, a number of injector-actuated syringes and powered injectors for pressurized injection of fluids, such as contrast media, have been developed for use in procedures such as angiography, computed tomography, ultrasound, and NMR/MRI. In general, these powered injectors are designed to deliver a preset amount of contrast media at a preset flow rate.
Angiography is used in the detection and treatment of abnormalities or restrictions in blood vessels. In an angiographic procedure, a radiographic image of a vascular structure is obtained through the use of a radiographic contrast medium, sometimes referred to simply as contrast, which is injected through a catheter. The vascular structures in fluid connection with the vein or artery in which the contrast is injected are filled with contrast. X-rays passing through the region of interest are absorbed by the contrast, causing a radiographic outline or image of blood vessels containing the contrast. The resulting images can be displayed on, for example, a video monitor and recorded.
In a typical angiographic procedure, the medical practitioner places a cardiac catheter into a vein or artery. The catheter is connected to either a manual or to an automatic contrast injection mechanism. A typical manual contrast injection mechanism includes a syringe in fluid connection with a catheter connection. The fluid path also includes, for example, a source of contrast, a source of flushing fluid, typically saline, and a pressure transducer to measure patient blood pressure. In a typical system, the source of contrast is connected to the fluid path via a valve, for example, a three-way stopcock. The source of saline and the pressure transducer may also be connected to the fluid path via additional valves. The operator of the manual system controls the syringe and each of the valves to draw saline or contrast into the syringe and to inject the contrast or saline into the patient through the catheter connection. The pressure transducers used in such procedures are extremely sensitive to even moderately high pressures generated during activation of the syringe, so the operator must close a valve to isolate the pressure transducer from the fluid path when the syringe is activated to prevent damage to the pressure transducer. While the syringe is not activated, the valve is usually open to monitor patient blood pressure.
The operator of the syringe may adjust the flow rate and volume of injection by altering the force applied to the plunger of the syringe. Manual sources of fluid pressure and flow used in medical applications such as syringes and manifolds thus typically require operator effort that provides feedback of the fluid pressure/flow generated to the operator. The feedback is desirable, but the operator effort often leads to fatigue. Thus, fluid pressure and flow may vary depending on the operator's strength and technique.
Automatic contrast injection mechanisms typically include a syringe connected to a powered injector having, for example, a powered linear actuator. Typically, an operator enters settings into an electronic control system of the powered injector for a fixed volume of contrast and a fixed rate of injection. In many systems, there is no interactive control between the operator and the powered injector, except to start or stop the injection. A change in flow rate in such systems occurs by stopping the machine and resetting the injection parameters. Automation of angiographic procedures using powered injectors is discussed, for example, in U.S. Pat. Nos. 5,460,609; 5,573,515; and 5,800,397.
U.S. Pat. No. 5,800,397 discloses an angiographic injector system having high pressure and low pressure systems. The high pressure system includes a motor-driven injector pump to deliver radiographic contrast under high pressure to a catheter. The low pressure system includes, among other things, a pressure transducer to measure blood pressure and a pump to deliver a saline solution to the patient as well as to aspirate waste fluid. A manifold is connected to the syringe pump, the low-pressure system, and the patient catheter. A flow valve associated with the manifold is normally maintained in a first state connecting the low pressure system to the catheter through the manifold, and disconnecting the high pressure system from the catheter and the low pressure system. When pressure from the syringe pump reaches a predetermined and set level, the valve switches to a second state connecting the high pressure system/syringe pump to the catheter, while disconnecting the low pressure system from the catheter and from the high pressure system. In this manner, the pressure transducer is protected from high pressures. However, compliance in the system components, for example, expansion of the syringe, tubing, and other components under pressure, using such a manifold system can lead to a less than optimal injection bolus. Moreover, the arrangement of the system components of U.S. Pat. No. 5,800,397 results in relatively large amounts of wasted contrast and/or undesirable injection of an excessive amount of contrast when the low pressure, typically saline, system is used.
The injector system of U.S. Pat. No. 5,800,397 also includes a handheld remote control connected to a console. The control includes saline push button switches and a flow rate control lever or trigger. By progressive squeezing of the control trigger, the user provides a command signal to the console to provide a continuously variable injection rate corresponding to the degree of depression of the control trigger. U.S. Pat. No. 5,916,165 discloses a handheld pneumatic controller for producing a variable control signal to control a rate of fluid dispersement to the patient in an angiographic system. U.S. Pat. No. 5,515,851 discloses an angiographic system with a finger activated control pad to regulate the injection of fluids.
U.S. Pat. No. 5,840,026 discloses an injection system in which an electronic control system is connected to the fluid delivery system and a tactile feedback control unit. In one embodiment, the tactile feedback control unit includes a disposable syringe that is located within a durable/reusable cradle and is in fluid connection with the fluid being delivered to the patient. The cradle is electrically connected to the electronic control system and is physically connected to a sliding potentiometer that is driven by the plunger of a disposable syringe. During use of the injection system of U.S. Pat. No. 5,840,026, the operator holds the cradle and syringe and, as the operator depresses the sliding potentiometer/syringe piston assembly, the plunger is moved forward, displacing fluid toward the patient and creating pressure in the syringe. A sliding potentiometer tracks the position of the syringe plunger. The electronic control system controls the contrast delivery system to inject an amount of fluid into the patient based on the change in position of the plunger. As the fluid is injected, the pressure the operator feels in his or her hand is proportional to the actual pressure produced by the contrast delivery system. The force required to move the piston provides the operator with tactile feedback on the pressure in the system. The operator is able to use this feedback to ensure the safety of the injection procedure. Unlike the case of a manual injection system, the injection system of U.S. Pat. No. 5,840,026 does not require the operator to develop the system pressure and flow rate. The operator develops a smaller, manually applied pressure that corresponds to or is proportional to the system pressure. The required manual power output, that is pressure X flow rate, is decreased as compared to manual systems, whereas the tactile feedback associated therewith is retained.
Medical connectors are commonly used in fluid delivery systems, as described above, for establishing the various fluid connections necessary in the system. For example, the indwelling cardiac catheter typically comprises a medical connector for connecting the catheter to medical tubing which associates the catheter to the source of contrast injection fluid, typically a syringe, and the source of saline. A typical catheter connector includes a female luer with a threaded tip adapted to receive a male luer surrounded by an annular member including corresponding threads on an inside surface thereof. Traditional medical connectors are also used at other fluid connection points in fluid delivery systems, such as to make connections in the low pressure system used to deliver saline to the catheter and, thus, to the patient. Such traditional medical connectors typically include either a threaded connection or a friction fit coupling to connect sections of tubing or other tubular devices such as needles and syringes. In a threaded connection, at least one part of the medical connector includes threads and the other part includes threads or lugs that are received in the threads. One part is turned relative to the other to make the connection. This type of medical connector is prone to unintentional decoupling. In a friction fit coupling, a male fitting having a frustoconical shape is typically inserted into a female fitting having a frustoconical-shaped receiving cavity. Opposing conical surfaces on the female and male fittings come into contact with each other and form a friction fit. This type of medical connector is also susceptible to accidental decoupling.
In view of the number of fluid connections required in, for example, an angiographic fluid delivery system, it is important to ensure that the medical connectors remain connected, particularly those in the high pressure system for the safety of attending medical personnel and the patient. In particular, due to the high pressures associated with angiographic contrast injection procedures, it is important to have, for example, a secure connection between the indwelling catheter and the fluid delivery tubing (i.e., fluid path) connected to the contrast delivery syringe. An accidental disconnection of the catheter can lead to many serious problems including loss of blood and contamination of the surroundings and/or medical personnel and the cessation of fluid delivery to the patient.
Typical “standard”, threaded or friction fit, medical connectors are often limited to use at relatively low pressures. Angiographic procedures often require the delivery of contrast to a patient at pressures of approximately 300 psi and higher. Although “high pressure” medical connectors are known in the medical field for use with high pressure medical tubing, such high-pressure medical connectors remain susceptible to ruptures and other problems and are not typically designed to be aseptic. Moreover, it is common to use fluid delivery systems to deliver fluids to patients at both low and high pressures. However, typical specially-designed high pressure medical connectors are not adapted to mate with both other corresponding high pressure connectors and conventional or standard “low pressure” medical connectors, thus limiting their utility as a “multi-purpose” connector.
Accordingly, a need exists for a secure fluid delivery system and fluid path that includes medical connectors that are suitable for use at relatively high pressures and which can accept both standard or conventional medical connectors and medical connectors specifically adapted for use at high pressures.